The present invention relates to a single crystalline fibrous superconductive composition and a process for preparing the same.
Since the discovery of high temperature superconductors based on a metal oxide (hereinafter referred to briefly as the "oxide"), practical application of such superconductors is under active research and development in a wide variety of fields.
More specifically, for example, the techniques of fabrication of thin films of oxide superconductive materials are necessary for producing devices for computers and the like wherein SQUID (superconducting quantum interference devices) or Josephson devices are used. As to the fabrication of thin films, it is reported that a grain boundary-free single crystalline thin film having sufficiently practical characteristics including a critical current density of higher than about 10.sup.6 A/cm.sup.2 can be formed by the sputtering method, the vacuum evaporation method, the CVD method or the like.
Meanwhile, in the fields of application of an oxide superconductor to the storage and transmission of electric energy, creation of a strong magnetic field, etc. wherein the characteristics of the oxide superconductor is utilized, the fabrication of wires from such an oxide superconductor is necessary. Attempts to fabricate wires from an oxide superconductor include the method wherein a calcined oxide superconducting powder packed in a silver sheath is heat-treated again, the sol-gel method, the method wherein a suspension of an oxide superconducting powder in a solution of a polymer is used to draw wires therefrom, and the method wherein a molten oxide superconductor is drawn into wires.
However, wires fabricated by any of these methods are in the form of a low-density polycrystalline substance with grain boundaries without exception. Thus, no wires having a practical level of characteristics have been produced yet. Furthermore, such wires have defects of brittleness, poor processability, low bending strength, etc., which are inherent in polycrystalline substances.